The fluid wall shear stress (WSS) driven by blood flow and the solid circumferential strain (CS) and associated circumferential stress driven by blood pressure act simultaneously on endothelial cells (ECs) lining blood vessels to modulate their phenotype. In recent dynamic computer simulations we showed that CS and WSS are most asynchronous (out-of-phase temporally) in precisely those regions of the circulation where atherosclerotic disease is most prominent (e.g., coronary arteries, carotid sinus). Our recent in vitro experiments have revealed a striking gene expression profile that is pro-atherogenic when CS and WSS are imposed asynchronously. We have observed a similar gene expression profile in the coronary arteries of rabbits. However, most studies of hemodynamic forces and atherogenesis have suggested that certain characteristics of WSS by itself induce an atherogenic phenotype without reference to CS or the interaction of CS and WSS. In the proposed research we will pursue the following studies in order to demonstrate the crucial role of the combined forces of CS and WSS and their phasic relationship in generating an atherogenic phenotype in endothelial cells in discrete regions of the circulation: 1. ECs grown on the inner surfaces of elastic tubes will be exposed to combined CS and WSS either synchronously or asynchronously, with a mean WSS that is either high or low. Gene expression profiles (48 genes) and EC turnover rates will be compared. The hypothesis is that asynchrony of forces will dominate mean WSS level in controlling EC phenotype. 2. The detailed biomolecular mechanism by which the eNOS gene is regulated when WSS and CS are applied synchronously or asynchronously will be determined as a first step toward understanding how these forces conspire to control EC phenotype. 3. The gene expression profiles (48 genes) of rabbit coronary arteries and carotid bifurcations (atherogenic) and common carotid arteries and femoral arteries (non-atherogenic) will be compared. The nutraceutical, conjugated linoleic acid (CLA), that was able to normalize atherogenic gene expression profiles in vitro, will be tested in the rabbit model to determine whether it can similarly alter EC phenotype in vivo. Project Narrative: The research is important to public health because it will determine which fundamental aspect of the mechanical environment of endothelial cells predisposes certain vessels (e.g., coronary arteries) to cardiovascular disease. In addition, the research will consider for the first time the possibility that pharmaceutical agents may normalize the pro-atherogenic endothelial phenotype induced by the mechanical environment inherent in the design of the cardiovascular system. This could ultimately lead to new drugs for the treatment of cardiovascular disease.